Pediculosis is a scalp infestation produced by Pediculus humanus capitis. Cases of pediculosis are quite frequent, both in their endemic and epidemic forms. As the lice feed on human skin and blood, they inject their digestive juices and fecal material into the skin. These materials, as well as the puncture wound itself, cause skin irritation and lesions from the resulting scratching, and can cause a serious infection with ganglionic inflammation. Lice are also vectors of certain diseases, such as exanthematic or epidemic typhus and recurrent fever.
The adult female louse has a life span of about one month and lays up to ten nits a day which are firmly attached to hair through an excreted cement. The nits hatch to release instars in about seven to nine days, and the instars become mature adults in another week. To cure someone of head lice requires an approach that eliminates all 3 stages of the louse life cycle.
Many currently utilized treatment methods are based on the application of pediculicides, which are toxic pharmaceutical agents that, when internalized, poison and kill lice. Typically, such pediculicidal agents enter via the respiratory spiracles, and once inside the louse, interfere with the function of a critical metabolic or physiological pathway, leading to death. Malathion, for example, inhibits acetylcholinesterase, disrupting signaling in the nervous system.
Examples of insecticidal agents used to treat lice are described in EP 0191236 and U.S. Pat. No. 5,288,483. A significant disadvantage of using these agents is that lice can become resistant. The need for further treatment increases the exposure to these harsh agents and increases the cost. Additionally, clinicians and parents are reluctant to treat children with agents that can also prove toxic to human beings. There are reports in the medical literature, for example, that children treated with lindane have developed seizures.
Moreover, many of these compounds have unpleasant odors or other undesirable properties, causing noncompliance by the patient, leading to re-infestation of the individual, and spreading of the infestation to others. In addition, the harshness of these agents make them unsuitable for use as prophylactics.
Home remedies such as application of corn oil, olive oil, eucalyptus oil, neem oil, coconut oil, mayonnaise, or petroleum jelly for a period of time sufficient to kill the lice (e.g. overnight) are not practical or completely effective.
A further disadvantage of prior methods is the requirement of removing the nits from the hair in a separate treatment step. The removal of nits has typically been done by hand using special fine-tooth combs. U.S. Pat. No. 4,927,813 teaches compositions containing formic acid that facilitate removal of nits from the hair; however, formic acid is a known caustic agent.
Use of combing alone to treat head lice has the disadvantage that the lice can hold onto the hair shafts using their claws or escape by crawling away from the area being combed. This labor intensive method requires daily combing, is painful, and is unpleasant since the lice are active, visible and crawling.
Heat has also been suggested as a means of killing head lice. However, its use has not been effective, due in part to the fact that crawling lice will rapidly move away from the heat source. Moreover, the temperatures needed to kill the lice, typically 140.degree. F. or higher, can burn or scald the scalp.
The use of heat in conjunction with pediculicidal compositions is discouraged. Not only are some of the solvents used in the pediculicidal compositions inflammable at the temperatures necessary to kill the lice, but the heat may additionally degrade the active pediculicidal agents as well.
Thus, there remains a need in the art for methods and kits useful for treating and removing lice infestations that are easy to use, inexpensive, cosmetically attractive and effective against lice resistant to other treatments. Moreover, there remains a need for methods and kits that eradicate nits as well as adults and instars, and that can be used prophylactically to prevent initial infection or re-infestation. Accordingly, these are some of the objects of the present invention.